We have a back patio with colored concrete that was poured last year. When the concrete was poured, it looked like the color was only picked up by the first half of the pour. The contractor poured the concrete mid-day when it was at least 110 and ended up not doing a proper finish because it was too hot for them to keep working. The result was the concrete ended up with slurry and trowel marks everywhere.
The contractor attempted to fix the concrete by putting some type of sealer over the top which ended up looking even worse.
What can we do (besides pulling everything up and re-pouring the concrete) to seal the concrete properly and get rid of the blemishes (see photos)?
From the photos, you can see the sealer splashes, improper broom marks, chipping everywhere, etc…
Click an image to see it full-sized.
Best Answer
I'm not a concrete expert, but if you don't mind a little extra height (which is often good for aesthetic and drainage reasons,anyway) you might try:
Sandblast the crud off of the top layer of the slab. You want to leave the surface roughened too, and sandblasting accomplishes both.
Was the old slab reinforced with mesh or rebar? If not, then maybe lay some reinforcing mesh down now. If it was me, I'd use concrete screws to fasten it, every couple of feet.
Saturate the old concrete with water, so it doesn't "rob" the new concrete while it's curing.
Pour at least an inch of "topping" or small-aggregate concrete.
Finish to taste.
It's probably best to test everything on one slab first, to see how it goes. See this article for another take on it.
If you do mind the extra height, sandblast and wet, but just use a thin layer of proper topping or finishing cement. Don't be surprised if it doesn't hold-up as well, though.
Just about any hardware store carries "Topping" cement. A very common product is QUIKRETE® Topping Mix. Note that it requires an additional "Acrylic Fortifier" if you use it only in a thin layer.
For an even thinner overlay, there are "skim coat" products like "SonoSkim Concrete Surface Finishing". I've never seen one of these hold up in high traffic areas, but you can reapply it as needed.